Filter apparatus



4, 1957 G. A. STEINTVEIT 3 9 FILTER APPARATUS Filed Feb. 25, 1964 INVENTOR:

GEORG A. STEINTVEIT QJMJSAUIAV ATTORNE YS United States Patent O 3,300,052 FILTER APPARATUS Georg Andreas Steintveit, Eitrheim, Odda, Norway, assignor to Porritts & Spencer Limited, Helmshore, Rossendale, Lancashire, England, a British company Filed Feb. 25, 1964, Ser. No. 347,221 7 Claims. (Cl. 210-402) The prese-nt invention relat-es to apparatus for the filtration of solids from fluids of the type in which a perforate filter drum is clothed externally with flexible filter sheet material.

The invention is concerned with the problem of securi-ng the filter sheet material to the exterior of the drum. In apparatus for the Vacuum filtering of solids from liquids, and in which .a rotatable filter drum is employed, two common methods are at present in use. 'One is by binding the sheet material onto the dr-um with wire wo-und helic-ally around the drum. The helical convolutions of the wire interfere with the removal of -the cake from the drum because of the obstruction presented by the wire oonvolutions. Furthenm-ore the application of internal air ressure to assist in removal of the cake :gives rise to bellying of the filter sheet material between the wire convolutions and to a concentration of stress in the filter material in the locality of the wire given rise to Wear and earlier failure of the filter material than might otherwise have been the case. With this method it has been found difficult to remove the cake from the immediate proXimity of the Wire and there has been a tendency for cake material to remain on the filter material adjacent t-o the wire.

The second method is by panel caulking. In this method the drum is aXially grooved at circumferentially spaced i-ntervals. The cloth is laid over the drum and forced into the axial -grooves and held in place by caulking material such as rope or lead strip. The distadvantage of this method is that the caulking is relatively insecure and tends to damage the cloth. 'More-over it limits the degree of air pressure that can be applied internally for removal of the cake.

Both methods are time consumi-ng and according to the size of drum .may :Occupy from 4 to 16 hours per filter; for example a drum of 12' length and 4' diameter may occupy 4 hours; a drum 18' long by 16' diameter may take 16 hours to clothe by either method.

In a .filter apparat us according to the present invention the drum is provided With circumferentially spaced axial grooves of outwardly converging or dovetail crosssection and the filter sheet material is held in position in each groove by a pair of wires or rods (herein-after referred to as -r-ods) which are held apart at opposite sides of the groove by spacers which are notched t-o receive the rods at opposite sides thereof.

The ,spacers may be of any suitable fonm but a pre- :ferred *form of spacer is cylindrical with *an annular recess of arouate secti-on at one end there-of servin-g -as a notch in which the rods are received. Each .spacer may have a substantially diametral hole therethrough -at its other end to receive a tool t-o facilitate its insertion between the rods in a groove. The tool may comprise a handle with a cranked arm extending therefrom adapted to fit in the hole in the spacer.

In one preferred *form of construction each groove is about 13 m-illimetres deep, about *9 m-illimetres wide at its mouth -and about 16 millimetres wide at its wider inner end or base, the corners of the groove at the mouth having a radus of about 2 millimetres. The rodes are preferably Stiff but resilie-nt and of Stainless steel and of a diameter about 4 millirnetres. The overall depth of the spacers should :be less than the depth of the 'grooves and ice for grooves as referred to above their overall depth should be about 10 millimetres. The size -of the notched part of each spacer should be such as to held the rods apart so that a loop of the filter material passing :around the two rods is su-bstantially wider than the width of the groove at its mouth.

The present invention renders it readily possible to clothe a filter drum with a relatively heavy openweave backing cloth and a lightweight closeweave top cloth.

The invention therefore includes a filter drum clothed with a relatively heavy openweave backing cloth and a lightweight -closeweave top cloth Which pass around pairs of rods located in dovetail section :axial grooves in the drum and held -apart in the grooves by notched spacers.

The edges of the filter cloth may :be secured to the margins of the drum in conventional manner by convolutions of binding Wire hut alternatively they may -be held in position by pairs of curved rods :and spacers disposed in ciroum-ferential grooves of dovetail section in the cylindrical outer face of the drum cr in the side face of the drum adjacent t-o the .cylindrical surface thereof.

The invention further-more includes a spreading tool for forcing the rods apart in the groove to enable spacers to be entered there/between and comprising a bar having opposed flat faces gradually approaching 'one another towards one end of the bar to render the bar :g-radually thinner towards that end and formed immediately adjacent that end with opposed notches which reduce the width of the flat faces.

The invention is further described by way of example with reference to the accornpanying drawi ngs in which:

FIG. l is an aXial sectional view illustratin-g an -aXial -groove in a filter drum 'according to the .invention with clothing secured therein;

FIG. 2 is a dia-grammatic fragrnentary view ill-ustrating a portion of a filter drum according to the invention;

FIGS. 3 -and 4 illustrate spreading tools.

The drum 1 has a series of aXially directed grooves 2 therein of dovetail section. The clothing of the drum comprises a relatively heavy openweave base cloth 3 and a lightweight closeweave top cloth 4. A loop 5 of the clothing is held in grooves 2 by a pair of Stainless steel rods 6 which are held apart by spacers 7. The length of the rods 6 is equal to Or very slightly less than the length of the drum i.e. of the length of the groove 2.

The spacers 7 each comprise a cylindrical body part 8 and a shank 9 at one end thereof in which is formed an annular recess 10 of arcuate cross section in Which the rods 6 are received. The body part 8 of the spacer is formed With a diametral hole 11 therethrough to receive a tool for facilitating the insertion of the spacer between the rods 6 in the groove.

FIGS. 3 and 4 illustrate spreading tools 15, 16 for forcing the rods 6 apart to enable the spacers 7 to be inserted therebetween. The tool 15 comprises a bar which at one end has opposed flat faces 17 which are inclined towards one another towards the end 18 in the fashion of a chisel. Notches 19 are formed in the tool irnmediately adjacent to the end 18 so as locally to reduce the Width of the faces 17.

The tool 16 has similar inclined faces 20 and notches 21 but the faces 20 are somewhat more widely spaced apart than faces 17 to render the tool thicker at its end 22 and the maximum width of the tool between the notches 21 is somewhat greater than between the notches 19.

In clothing a drum according to the present invention the rods 6 are pressed down onto the bottom face 24 of the groove 2 by a flat ended presser which may be of wood and may be of tapered wedge like form. While the rods are so held on the bottom 24 of the groove the end 18 of the tool 15 s inserted between the rods and turned through 90 to spread the rods apart between the notches 19 of the tool. The end 22 of tool 16 is then inserted between the rods and turned through 90 to spread the rods still further apart whereupon a spacer can be inserted between the rods. The tool 16 again turned through 90 to release it from between the rods and to permit the rods to engage against opposite sides of the annular recess '10. In this way the spacer is looked between the rods and the rods are locked in the groove.

Spacers should be provided at appropriate intervals along the groove say at intervals of 6, 8 or 10 -nches acoording to the size of drum, size of groove, weight of filter clothing and stiifness of the rods 6.

I claim:

1. A perforate filter drum of the type which is clothed externally with flexible filter sheet material comprising a' drum provided with circumferentially spaced axial grooves of outwardly converging dovetail cross-section, a pair of rods in each of said grooves holding the filter 'sheet material therein and spacers between the rods of 'each pair to hold the 'rods apart at opposite sides of the groove, said spacers being notched to receive the rods at opposite sides thereof. 4

2. A perforate filter drum of the type which is clothed externally with flexible filter sheet material, in which the drum is provided with circumferentially spaced axial grooves of outwardly convergng dovetail cross-section and the filter sheet material is held #in position in each groove by a pair of rods which .are held apart at opposite sides of the groove by spacers which are notched to receive the rods at opposite sides thereof.

3. A filter drum according to claim 2, comprising spacers which are cylindrical with an annular recess of arcuate section at one end thereof serving as a notch in which the rods are received.

4. A filter drum according to claim 3, in which each spacer has a substantially diametral hole therethrough to receive a tool to facilitate its insertion between the rods in a groove in the drum.

5. A filter drum according to claim 2, in which the grooves are about 13 mm. deep, about 9 mm. wide at the mouth and about 16 mm. wide at the base.

6. A filter drum according to claim 5, in Which the rods are about 4 mm. in diameter.

7. A perforate filter drum accord-ing to claim 2 clothed with a heavy openweave backing cloth and a lightweight closeweave top Cloth which pass around the said pairs of rods located in the axial grooves in the drum and held apart in the grooves by said notched spacers.

References Cited by the Examiner UNITED STATES PATENTS 1,276,163 8/1918 Biesel 210-402 X l,348,036 7/ 1920 Mount 210-404 2,055,251 9/1936 Duvall 210-404 2,145,933 2/ 1939 Kehrer 210-402 2,877,877 3/1959 Davis -395 X REUBEN FRIEDMAN, Primary Exam'z'ner.

SAMIH N. ZAHARNA, J DE CESARE,

Assismnt Examiners. 

1. A PERFORATE FILTER DRUM OF THE TYPE WHICH IS CLOTHED EXTERNALLY WITH FLEXIBLE FILTER SHEET MATERIAL COMPRISING A DRUM PROVIDED WITH CIRCUMFERENTIALLY SPACED AXIAL GROOVES OF OUTWARDLY CONVERGING DOVETAIL CROSS-SECTION, A PAIR OF RODS IN EACH OF SAID GROOVES HOLDING THE FILTER SHEET MATERIAL THEREIN AND SPACERS BETWEEN THE RODS OF EACH PAIR TO HOLD THE RODS APART AT OPPOSITE SIDES OF THE GROOVE, SAID SPACERS BEING NOTCHED TO RECEIVE THE RODS AT OPPOSITE SIDES THEREOF. 